'This Is Us' Stars and Creator Break Down 'Special' Jack-Rebecca Flashback Episode: It Was a 'Magic Moment'

This Is Us continues to astound us, and Tuesday’s episode was no different.

The beloved family drama broke with convention in its latest installment -- even This Is Us has storytelling guidelines, however fluid they may be -- with an entire episode spent on the hours leading up to The Big Three’s births in the pilot. It’s in this episode, titled “The Big Day,” where we learn the heartbreaking backstories of the fireman who found Randall and Dr. K’s grief, as well as Jack and Rebecca’s big fight hours before she went into labor.

Creator Dan Fogelman pointed to this episode as holding particular importance to him -- not because of the slight risk involved airing it as the 12th episode, but because of the added context it provided to the arcs of characters we’ve grown to cherish. It was after watching a tiny indie film one year at the Sundance Film Festival that Fogelman was inspired to revisit the past.

“Such a big part of the show is the lack of a beginning and an end. It’s time being this object that doesn’t operate in a straight line,” Fogelman tells ET. “My hope was always, if we start the pilot as a starting point and then broke the rules of time a little bit as we jump all over the place, how interesting would it then be to go back to where we met these people and see them in that timeline before we enter watching [the show].”

Ancillary characters such as the fireman, and less so Dr. K, became pivotal ingredients in the fabric of Jack and Rebecca’s lives. Without them, the episode suggests, their lives would look -- quite literally -- different.

“I always had the idea of Dr. K and the fireman coming back and seeing how they got there that day and the sliding doors of life,” Fogelman says, praising the actor who plays the fireman, Brian Oblak. “He had two lines, three lines in the pilot and then we tracked him down and called him. He was so excited to do this and he did such a great job.”

For Milo Ventimiglia and Mandy Moore, retracing the steps that led to The Big Three’s births was, in itself, “special” and “fulfilling” to experience as actors.

“To revisit what was already a magic moment in anyone’s life, it’s fun,” Ventimiglia tells ET. “How the writers were able to weave [the storyline] and it doesn’t follow the conventions of having to touch certain moments for each character, it felt like it was breaking the formula. I appreciate it and I respect what the writers were able to put together for this episode. I think it’s a pretty special episode that still moves forward the mission of telling a good story and displaying goodness, but at the same time, you’re getting into [it in] a completely side-swept way.”

“It was a trip down memory lane and it was very fulfilling,” Moore tells ET. “When Dan first told us about this ingenious idea, we were all really excited and intrigued: How is it going to work? How is it all going to cut together? It was all very seamless.”

It’s notable to add that none of the scenes or moments featured in the pilot -- i.e. the hospital, the birthday dance -- had to be reshot for the episode. Extra footage left unused were edited back in, which shows just how forward-thinking Fogelman was of the long-term narrative plan of This Is Us.

“When Milo comes in that we lost the third baby and I say, ‘That’s not true, that’s not true,’ that was actually from the pilot as well, but it was never in the episode. They just used a piece of it in the montage in the pilot,” Moore recalls, adding that the heartbreaking exchange was completely unscripted and a last-minute addition. “I don’t even know what I said. It was kind of thrown in at the last minute. To see it onscreen, I had no idea what I did or what I said because we’ve done so much since then! That was almost a year ago.”

The episode also drew upon the dichotomy between Rebecca’s insecurities of becoming a mother of three and the larger-than-life image of Jack as the ideal husband and father.

“For all the praise that Jack gets from his wife and his kids or even people on the audience side about what a great husband or father he is, Jack is still a flawed man and we will see that,” Ventimiglia says. “He has his demons, he has his battles, but he loves his wife and he loves his kids. He’s a very simple man in his life -- he loves his wife, he loves his kids -- that’s his world.”

“This is a woman, where we found out in the fifth episode, wasn’t even sure she wanted to be a mother, and then, suddenly to be a mother for three and have to come to terms with that and how utterly life-changing that’s going to be over the course of eight months -- it’s a lot,” Moore says.

“She’s drowning in her fears and her expectations and her anxiety,” she continues. “You couple that with Milo’s character, Jack, who is such a solid man in every imaginable way. He’s perfect, he’s unshakable. I’m sure it has her questioning, ‘Am I really suited for this role? He’s going to be great but I have my doubts about myself.’”

Ventimiglia admits that there’s a self-inflicted pressure to playing a character as widely adored as Jack, saying that while “it’s not easy, it’s not difficult” either. Moore notes that more of Jack’s skeletons (see: his alcoholism) come out as the 18-episode season starts to wind down.

“In his simplicity, he’s incredibly complex,” Ventimiglia says. “Particularly for Mandy and I, we have to be very aware and present in the moments we’re in and know what we’ve experienced as these characters leading up to that moment. With that being said, it’s being free with the words we’re given and free with the moment where you’re standing there with your co-star and you’re in a marriage and you’re with your kids and representing a good husband, a good dad. Jack has a straight road that he walks on and he doesn’t really fire too far off of it.”

“We’re shooting episode 15 right now and there are definitely issues that come to light that are not pretty and are traits of his that Rebecca is not attracted to and does not like at all,” Moore hints.